The optical transport network (Optical Transport Network, OTN in short) technology is a core technology of new-generation transport networks, which includes technical specifications of an electric layer and an optical layer and can implement flexible scheduling and management of large capacity services, and gradually becomes a mainstream technology of backbone transport networks.
At the beginning, the OTN standard (ITU-TG.709) defines 3 OTN containers: an optical channel data unit (Optical Channel Data Unit, ODU in short) 1, an ODU2, and an ODU3, the tributary slot types of which are all 2.5 Gb/s, and the rate levels of the ODU1, the ODU2, and the ODU3 are 2.5 Gb/s, 10 Gb/s, and 40 Gb/s respectively. The ODU1 includes 1 tributary slot, the ODU2 includes 4 tributary slots, and the ODU3 includes 16 tributary slots. The OTN standard is extended on the basis of the original standard to support Ethernet services and other new services and fit in with new application scenarios, and new types of signals are proposed, for example, an ODU0 (with a switching granularity of 1.25 Gb/s) suitable for transmitting low-speed signals, an ODU4 (with a switching granularity of 100 G) suitable for transmitting higher rates, an ODU2e, an ODU3e1, an ODU3e2, and a bandwidth-variable ODUflex.
To multiplex a low-rate ODU to a high-rate ODU for transmitting services, a multiplexing relationship between ODUs is further defined in the OTN standard. According to the multiplexing relationship, the ODUs are sorted into a lower order ODU (Lower Order ODU, LO ODU in short) and a higher order ODU (Higher Order ODU, HO ODU in short). A lower order ODU may be multiplexed into a higher order ODU, and encapsulated as an optical channel transport unit (Optical Channel Transport Unit, OTU in short) which is transmitted on a link. In the process of multiplexing the ODU, a tributary port number (Tributary Port Number, TPN in short) needs to be configured for two adjacent nodes manually in a network management system, so that the lower order ODU is multiplexed into the higher order ODU link, namely, an OTU link between the two adjacent nodes according to the assigned TPN. The TPN is configured manually on each link. Therefore, the TPN configuration involves a huge workload and a high error rate.